The White House increased security, and the Justice Department and FBI mobilized to fully investigate the explosions occurring near the Boston Marathon finish line

WANG YIOU — ZUMAPRESS.COM/MCT

WASHINGTON — The FBI arrested a Mississippi man Wednesday in connection with letters mailed to President Barack Obama and Republican Sen. Roger Wicker that tested positive for the poisonous substance ricin.

Agents arrested Paul Kevin Curtis around 5:15 p.m. EDT at his home in Corinth, Miss., alleging that he’s responsible for the mailings of three letters that contained a granular substance that preliminarily tested positive for ricin.

FBI officials said three letters were sent to Obama, Wicker and a Mississippi justice official identified by law enforcement officials only as a judge. Curtis, about 46 years old, wasn’t immediately charged.

The evening arrest capped a multi-agency investigation into a spate of potentially poison-laced letters and packages Wednesday meant for Obama and Wicker and the state official.

Investigators appeared to focus quickly on Curtis, who they believed sent letters with hateful rhetoric to members of Congress in the past. His wording was similar to the language in the new letters, said a law enforcement official familiar with the inquiry who spoke on the condition of anonymity because of the sensitive nature of the material.

In one of the letters, the official said, the mailer wrote, “No one listened to me before. This must stop. To see a wrong and not expose it is to become a silent partner to its continuance. I am KC and I approve this message.”

The arrest capped a two-day period in which the news of letters to Obama and Wicker containing the toxic and potentially lethal poison combined with Monday’s Boston Marathon bombings to put government offices on alert and on edge. Congressional offices in two Senate office buildings were cordoned off briefly over concerns about suspicious packages, and the offices of senators in Michigan and Arizona reported receiving suspicious letters. None of the others tested positive for ricin or other poisons, according to another law enforcement official, who lacked the authority to speak publicly and insisted on anonymity.

In Washington, a letter sent to Obama that was intercepted Tuesday at a remote Secret Service mail-screening center contained a granular substance that tested positive for potentially lethal ricin. The letter addressed to Wicker was intercepted at an offsite postal facility that screens congressional mail. It was unclear Wednesday whether the Mississippi judge personally received a letter.

“The envelope was immediately quarantined by U.S. Secret Service personnel, and a coordinated investigation with the FBI was initiated,” the FBI said of the Obama letter. “Anytime suspicious powder is located in a mail facility, field tests are conducted. The field and other preliminary tests can produce inconsistent results.”

While 24-hour tests at a Maryland laboratory confirmed that the three letters contained ricin, additional tests must be conducted to determine whether the substance was extracted in a way that enhanced its potency to make it truly dangerous if tiny amounts were inhaled or ingested, one of the law enforcement officials said.

Obama was briefed Tuesday night and again Wednesday morning. White House Press Secretary Jay Carney said the FBI hadn’t made any connection between the letters and the explosions Monday in Boston.

“Before we speculate or make connections that we don’t know exist, that the FBI has made a clear statement about, we need to get the facts,” Carney said.

In a statement, Wicker said that he and his wife, Gayle, "want to thank the men and women of the FBI and U.S. Capitol Police for their professionalism and decisive action in keeping our family and staff safe from harm."

"My offices in Mississippi and Washington remain open for business to all Mississippians," he said. "We particularly want to thank the people of Mississippi for their thoughts and prayers during this time.”

On Capitol Hill, law enforcement officials cordoned off sections of the Hart and Russell Senate office buildings Wednesday after suspicious envelopes were found on the third floor of each building and a package was found in the Hart atrium. The buildings, across the street from the Capitol, house the offices of senators.

The sectioned-off spaces were reopened Wednesday afternoon.

Authorities “have confirmed a deadly poison was discovered in at least two separated letters found at the White House and Capitol Hill mail facilities,” said Sen. Bill Nelson, D-Fla., a member of the Senate Intelligence Committee. He added that police also were questioning a man who had “numerous letters in a backpack.”

Sen. Joe Manchin, D-W.Va., whose gun control measure, co-authored with Sen. Patrick Toomey, R-Pa., was being debated on the Senate floor Wednesday, said his Hart building office had been quarantined.

Other lawmakers said they’d received suspect letters or packages.

Sen. Carl Levin, a Michigan Democrat who chairs the Senate Armed Services Committee, said his office in Saginaw, Mich., had received a “suspicious-looking letter” and had alerted authorities. “We do not know yet if the mail presented a threat,” Levin said in a statement.

A spokesman for Sen. Richard Shelby of Alabama, the ranking Republican on the Senate Appropriations Committee, reported that “the Capitol Police investigated a suspicious package in our office and have now given us the all clear.”

“Sen. Shelby and staff are unharmed,” spokesman Jonathan Graffeo said, referring all other questions to the Capitol Police.

Sen. Jeff Flake, R-Ariz., said an aide had discovered “suspicious letters” in his Phoenix office. No dangerous materials were found on the letters, said Genevieve Rozansky, Flake’s spokeswoman.

Curtis apparently authored a bizarre, rambling Internet posting a couple of years ago in which he alleged that he was terminated from a northern Mississippi hospital about a decade ago after finding body parts in a refrigerator in the facility’s “morgue.” He wrote that the episode resulted in three years of research leading to “countless court battles, cops harassing me weekly, death threats, personal & financial losses, several thefts, my home burned down, car exploded, marriage dissolved & bankruptcy.”

Curtis also said that he and his brother were “the only duo Elvis Presley Tribute act in the world.”

As he pursued his case, he wrote, “I sent letters to State Representative Roger Wicker, Senator Trent Lott and Thad Cochran. I never heard a word from anyone. I even ran into Roger Wicker several different times while performing at special banquets and fundraisers in northeast, Mississippi but he seemed very nervous while speaking with me.”

He said that when he brought up his case against the hospital, Wicker “would make a fast exit to the door.”

The spate of alerts Wednesday at the Capitol came a day after news that the letters to Wicker might have contained ricin. Two preliminary tests at an offsite mail-screening facility in suburban Maryland indicated the presence of ricin; two other tests were negative.

Senate Sergeant-at-Arms Terrance Gainer, a former second in command of the Washington Metro Police Department, urged calm and caution for Senate workers in dealing with mailed or delivered materials.

“All mail and commercial packages processed through the Senate mail facility have undergone rigorous testing through protocols established following previous anthrax and ricin attacks at the Senate,” Gainer said in a statement. “Mail delivery in Washington, D.C., offices will continue this afternoon – this mail was processed in advance of receipt of the suspicious ricin mailing, has been successfully inspected and tested, is completely safe and will be delivered by uniformed Senate post office employees.”

He warned that staffers shouldn’t open sealed envelopes and should accept items only from Senate post office employees or government couriers with government-approved identification.

Ricin, derived from castor beans, can be easily and inexpensively produced. Law enforcement and terrorism experts say it’s more effective on individuals than as a mass weapon. It takes only a small amount to kill a human, and there’s no specific test or antidote.

Ricin poisoning isn’t contagious. Touching the substance would cause little harm. But eating after touching ricin could be harmful.

According to the Centers for Disease Control and Prevention, unintentional exposure to ricin is highly unlikely. Death from inhalation or ingestion, if not quickly treated, could come within 36 to 72 hours, the CDC says.

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